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Freediving - Lung Squeeze
The following material has been written by experienced freedivers on the topic of lung squeezes, a terrible injury that appears to be more common that it may seen. It is worth taking these comments seriously.
Don't Get Squeezed!
Every year I before competition time I hear of people getting lung squeeze during their constant weight training. And every year I try to warn people to be safe and conservative when it comes to their lungs. A very few people take my general advice, but most do not assume responsibility for their own safety.
This year is no different.
I have tried to warn new freedivers that lung barotrauma is dangerous. Back in 2002 I experienced a horrible lung squeeze that convinced me that I would never dive deep again if I could not figure out how to avoid lung injury. I couldn't breathe properly for a month following my squeeze. But now I see that many freedivers who have been diving and competing for several years now have not understood the danger.
Squeeze is serious! You may have only felt discomfort and some wheezing and coughing up blood, but let me tell you from personal experience that it can get FAR WORSE (as if blood and coughing isn't bad enough). We don't know what the long term effects are of suffocating your alveoli in blood on a regular basis, nor do we no what the long term effects are of increasing your lung capacity through lung packing. I hear that one local freediver may have to give up his passion because of complications from lung packing techniques and squeeze. That is very sad news.
I guess the reality is that until you experience a horrible squeeze yourself, you won't listen to what I say. But before you ignore me for another competitive freediving season, and get squeezed again and again, please consider the effect this has on the freedivers you dive with, if you don't care about your own health and safety. It is scary to watch someone cough blood and turn blue. It would be even scarier if you drowned in their own blood while your friends or buddies watch you. It would be sad if you could not dive again because of long term effects from repeated squeezes.
It also sets a bad example for new freedivers around you. I am always disappointed when elite freedivers get squeezed at an international competition or world record event. They should know better. The attitude is usually so casual. "Oh yeah, I got squeezed but then I was fine." What does this say to someone wanting to "hit a new personal best," especially in the danger zone of 25-50 metres (for most new freedivers)? It makes it sound like squeeze is not serious at all, just part of "going for it."
If you squeeze your lungs you are an ignorant freediver. Plain and simple. It means you haven't spent the time to pay attention to how your body reacts to rapid changes in pressure, nor have you bothered to find out from others how to avoid it (or perhaps no one ever told you about the danger). I don't care if you are diving to 70m or 30m, a true expert, considerate of his or her own safety and considerate of his or her freediving buddies, friends, and family, will try figure out how to dive safely and without squeeze or not dive so deep.
Most people go too deep too fast. It is a tantalizing adventure, I know from my own experience. But we all know that most freedivers, even beginners, can hold their breath for long enough to reach depths much deeper than their lungs can handle.
Going deep requires time for your body to adjust. Not days, but months and even years. A mountain climber spends time at altitude to avoid altitude sickness and pulmonary edema. Freediving is the same, just in reverse. But whereas a mountain climber takes many hours or even days to reach 20,000 feet, which is a fraction of one atmosphere of pressure, freedivers can reach several atmospheres of pressure in under a minute.
My experience with avoiding squeeze has led me to a few conclusions:
- Packing is an advanced technique that may not be safe for everyone and requiring careful control so as not to injure lung tissue.
- Packing for dive can lead to squeeze for a variety of reasons, even in shallow depths
- Fast descents can increase severity and likelihood of lung injury
- Vaslava equalizing, contractions, or tension in the diaphragm (common among beginners and intermediate freedivers) can lead to squeeze
- Rapid depth progressions or big jumps in depth most often result in lung squeeze
- Those most at risk are usually intermediate freedivers who are confident that they can hold their breath long enough to go deeper than 35m.
In my own diving, I follow these rules:
- Never use lung packing while freediving (I have had to improve my equalizing techniques) and avoid excessive packing during static and dynamic
- Go down slowly at less than 0.8 m/s or even slower in the first 30m of each dive (for gradual acclimatization )
- Always allow enough time to achieve a certain depth goal (this is why I decided not to compete, because I had not done any dives over 40m since last summer and a few weeks was not enough to reach my goal)
So far in the last few years, this has allowed me to train effectively without squeeze. I know this may not work for everyone, but I challenge you all to find out what does work for YOU.
I have come to accept that perhaps due to my previous squeezes or other factors, I may not ever be able to reach depths deeper than my current personal best. I am happier to enjoy a long life of recreational dives rather than risking it all for one dive.
Failing these efforts to share my experience in the hopes that you will take measures to avoid future lung squeeze, I would like to propose that CAFA consider squeeze as a criteria for disqualifying or penalizing a performance. If safety is our mission, then I think it is appropriate. Perhaps this is the only way to get the message across.
I encourage CAFA members to give feedback for or against this proposal. I realize there may be complexities involved in defining "lung squeeze" for the purpose of judging. Or perhaps squeeze as a judging criteria is too problematic. Another option would be that competitors who obviously suffer a lung squeeze would be put on probation. If they get squeezed at any future competition, they will receive no points for their dive.
I am happy to share my ideas on how to reduce the risk of squeeze with anyone who is interested on this forum or by private email. Of course, if you have squeezed your lungs, please seek proper medical attention fro a diving medical doctor.
Co-Chair of CAFA Safety Committee
Hi Guys, a little note from the Tropics. I'll break my holiday for this subject.
According to an Apnea Acadamy doctor and instructor at least 50% of freedivers experience one or more squeezes at one point or another. 10% of them develop chronic problems which may get worse with every new squeeze. Some people have to quit the sport completely to avoid irreversible damage. There are clinically documented cases of experienced spearfishers getting squezeed at quotes as low as 10 mtrs.
My small survey of every divers I know and of divers at last year worlds seem to indicate the same statistics. Squeezing is VERY VERY common, people that not admit to it live in denial and are mis-leading new comers to the sport. In fact the majority of us will likely be squeezed sooner or later.
According to the best lung doctor I spoke to so far and contrary to popular belief, our lungs are not made to sustain freediving stresses. The interface between gas and liquid (blood) is extremely delicate.
It is time that the freedivers' dirtiest secret be uncovered. Let's face it and forget about the bad press.
Lung Squeeze factors: Packing, Residual Volume and Descent Rate
I am certain that there are other factors to take into consideration, as can be illustrated by the following example:
- Freediver A packs substantially, descends at an average speed of 1.0 m/s, lung volume is 8 Litres (extra 2 Litres of air from packing), residual volume is 1.5 Litres.
- Freediver B doesn't pack, descends at an average speed of 0.75m/s, lung volume is 6 Litres, residual volume is 1.5 Litres.
If we use, pV=K (Boyle's law) and expand to pressure (residual volume at depth) x Volume (residual volume at depth) = p (at surface) x Volume (of lungs at surface) and plug in the numbers, we see that:
- Freediver A reaches her residual volume of 1.5L at approximately 43.3m (5.3 atm) in a descent of 21.65 seconds.
- Freediver B reachers her residual volume of 1.5 L at a much shallower 30m (4.0 atm) in a descent of 22.50 seconds.
Given this math (noting that Boyle's is not perfectly accurate underwater), it seems a no brainer to choose packing over no packing, if you assume that problems with squeeze occur only AFTER residual volume has been reached (this idea may be wrong, see below). To take it one step further, the ultimate application of this method would be to have a lung volume like Hubert Maier's 14L which would allow him to reach residual volume of 1.5 L at 9.3 atm or 83m.
Also, in the real world, it is possible that both freedivers could get squeezed in this scenarios, depending on their levels of training and pressure adaptation. But let's assume for this example, that both freediver A and B are at risk of getting squeeze at or slightly beyond their residual volume of 1.5 Litres.
So, here's the scenario that I've had some experience with in the last four years:
- Both divers dive to just slightly more than their residual volume depth. Freediver A, packing an extra two litres, gets a lung squeeze at 45m . Freediver B, no packing, does not get squeezed at 32m. Why?
All other things being equal (impossible, I know), I believe that packing and descent speed are the most important factors related to squeeze, especially when developing adaptations at and beyond residual volume.
We know that packing exerts pressure on the lungs, heart, circulatory system, alveoli, chest wall, diaphragm, etc... I remember hearing of imaging done in Kona, Hawaii of freedivers using packing. Their hearts were squashed flat, apparently. When you pack, often your heart rate speeds up (heart cannot push as much blood with each stroke, so it increases stroke frequency, I think is the explanation). Also, many of us have experienced fading vision, dizziness or LMC from packing as the extra pressure in the lungs prevents blood from reaching the brain. There are also anecdotal reports of freedivers who have seen an increase in residual volume from excessive packing [ed: I am concerned that I, too, might fall into this category -Cal]. Tom Sietas believes this is why he gets squeezed at any dive beyond 70m. He has a lung volume of at least 12 Litres and growing, I believe, from all his static apnea training. I don't know what his residual volume is at now.
Now, why would Freediver A get squeezed at 45m? I can think of a couple of reasons:
If we accept that blood shift is a mechanism that protects us at depth from squeeze when we dive beyond our residual volume (otherwise we'd be toast!), then increasing the air pressure within the lungs with packing could inhibit blood shift toward the lungs in some way. If packing can cause LMC, blackouts and a squashed heart at sea level, then I think it is safe to assume that if will have some effect on you as you descend.
The most drastic change in lung volume is in the first 20m of the descent when you go from a full lung volume to one third that volume. For Freediver A, she does it in approx 10 seconds! As far as I know there are no specific studies on the rate of blood shift vs. lung volume, but I would guess that your circulatory system requires some time to adjust to the pressure change. For example, if any of us descended to 30m in 1 second, a squeeze would be highly likely. This is why negative pressure dives can be so dangerous. Exhale and drop and suddenly in a few seconds you are at 100m of pressure!
I also wonder also if the extra pressure in the lungs from packing does not drive away plasma from where it is needed, meaning that the body requires even more time to redirect it to the core. But in the time it takes to react to the ambient pressure change, Freediver A is already at 25m and still going down.
This idea implies that squeeze doesn't actually happen at residual volume. It is "set up" in the first 20m and going deeper than that just nails the coffin shut, so to speak. When you reach your residual volume, your blood shunt is still not quite adequate and squeeze ensues.
In addition to the delayed blood shunt caused by packing pressure in the lungs, I also believe that a rapid descent means that the ambient pressure increases too quickly for the blood shunt. If Freediver B, not packing, descended at 1.2 m/s, I would be afraid that she would also suffer a squeeze by not giving her body enough time to shunt blood to the core.
Also, packing can result in extra speed on the descent for inexperienced divers, as they struggle to overcome the extra buoyancy created by their over-inflated lungs.
WHY BEGINNERS AND INTERMEDIATE FREEDIVERS ARE AT HIGHER RISK
I think the reason so many freedivers put themselves at risk of squeeze is because lung packing and a rapid descent seem like solutions to simple problems: equalizing and fear.
Most new freedivers start to run out of equalizing air at around 25-30m. If they switch to Frenzel they might make it to 35m -40m. Doing Frenzel deeper than 40m requires either the mouthfill technique or excellent chest flexibility, which in turn requires much more diving experience than a novice would have.
Packing an extra litre or two immediately provides more air for all equalizing techniques. Suddenly, 45m-50m is not impossible at all, even with a crappy equalizing technique. It is common for freedivers to progress from 30-45m very quickly. Ten metres jumps in depth in a weekend are not unheard of. But often squeeze happens as well.
Excessive descent speed reflects the fear a freediver has with a new depth or pb. If she were completely comfortable, Freediver A would realize that there's no rush and that a slower, relaxed descent is more efficient. But often the impulse is to make the depth as fast as possible and get the hell back to the surface! At my first nationals in 2001, I sprinted to 46m and suffered a moderate squeeze (coughing blood, wheezing). The dive, if I remember correctly was probably around 1'20" or less. Now it takes me over 1'30" to reach 60m on the descent alone and no squeeze.
Diving deep without packing is possible. All it takes is more time to adapt and equalizing skill. (Umberto Pelizzari dove over 80m without packing.)Cheers, Pete